1. Field of the Invention
The present invention relates to a hydrogen supply apparatus and a hydrogen supply method used when measuring fuel consumption of a hydrogen fuel vehicle.
2. Description of the Related Art
In recent years hydrogen has become the focus of attention as a clean fuel without discharge of atmospheric pollutants. Vehicles obtaining their driving force from hydrogen such as fuel cell vehicles provided with fuel cells, and hydrogen engine vehicles mounted with hydrogen engines, and the like, employing hydrogen as fuel are under development.
As a method for measuring fuel consumption of such vehicles employing hydrogen as fuel (hereafter referred to as “hydrogen fuel vehicles”) there is the weight method.
The weight method measures the mass of hydrogen fuel directly with a scale. In practice, hydrogen is supplied from a measurement hydrogen tank to a vehicle on a chassis dynamometer, the vehicle is run on the chassis dynamometer, the mass of the hydrogen tank before and after the test is measured, and the fuel consumption is measured from the mass difference. This weight method has few factors giving rise to errors, and high accuracy of measurement can be obtained with the use of an accurate scale.
Furthermore, the flow method, the P/T method (pressure method), and the electric current method are available as other methods for measuring fuel consumption of hydrogen fuel vehicles.
The flow method constantly measures and integrates the flow of the supplied hydrogen to measure fuel consumption. The P/T method measures the pressure and temperature of the hydrogen tank used before and after the test and computes fuel consumption from gas phase equations and the like. The electric current method employs the principle that the current output from a fuel cell stack is proportional to the fuel consumption used for power generation, integrates the value detected by an ammeter, and computes the fuel consumption. These methods of measurement have a variety of problems, and generally cannot be considered superior to the weight method.
Moreover, documentation related to methods of measuring fuel consumption of hydrogen fuel vehicles, for example, non-patent document 1, is available.
[Non-patent Document 1]
E. Kuroda et al, ‘An Investigation of Methods for Measuring Fuel Consumption of Direct Hydrogen Fuel Cell Vehicles’, JARI Research Journal, 2002, Vol.24, No.10, pp 49–54
While the weight method provides high accuracy of measurement, the points hereunder required improvement.
When the measurement hydrogen tanks are connected to the piping for connection to the test vehicle (hydrogen fuel vehicle) while the piping contains air, hydrogen from the measurement hydrogen tanks fills the piping at the start of the test, thus drawing out hydrogen from the measurement hydrogen tanks so that hydrogen filling the piping is not consumed by the test vehicle, giving rise to an error in fuel consumption.
Furthermore, the pressure of the measurement hydrogen tanks may be reduced when hydrogen from the measurement hydrogen tanks is consumed in the test, altering the amount of hydrogen filling the piping and thus giving rise to an error in fuel consumption.